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How to Figure Out a Stem and Leaf Plot

How to Figure Out a Stem and Leaf Plot

How to Figure Out a Stem and Leaf Plot

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A stem and leaf plot is a term in data visualization with roots in political science, journalism, and applied statistics. It's a way of representing the relationship between two categories in a two-dimensional space. In this article, we'll give you an introduction to this design approach, and how you can use it in your report.

Stem

Analyse Elliot's stem and leaf plot. What is his most common score on the geography quizzes? What is his highest score? His lowest score? Rotate the stem and leaf plot onto its side so that it looks like a bar graph. Are most of Elliot's scores in the 10s, 20s or under 10? It is difficult to know from the plot whether Elliot has improved or not because we do not know the order of those scores. Each morning, a teacher quizzed his class with 20 geography questions. The class marked them together and everyone kept a record of their personal scores. As the year passed, each student tried to improve his or her quiz marks. Every day, Elliot recorded his quiz marks on a stem and leaf plot. This is what his marks looked like plotted out:

The main advantage of a stem and leaf plot is that the data are grouped and all the original data are shown, too. In Example 3 on battery life in the Frequency distribution tables section, the table shows that two observations occurred in the interval from 360 to 369 minutes. However, the table does not tell you what those actual observations are. A stem and leaf plot would show that information. Without a stem and leaf plot, the two values (363 and 369) can only be found by searching through all the original data—a tedious task when you have lots of data! (Source: www150.statcan.gc.ca)

Use

A stem-and-leaf plot is a way to plot data and look at the distribution. In a stem-and-leaf plot, all data values within a class are visible. The advantage in a stem-and-leaf plot is that all values are listed, unlike a histogram, which gives classes of data values. A line graph is often used to represent a set of data values in which a quantity varies with time. These graphs are useful for finding trends. That is, finding a general pattern in data sets including temperature, sales, employment, company profit or cost over a period of time. A bar graph is a chart that uses either horizontal or vertical bars to show comparisons among categories. One axis of the chart shows the specific categories being compared, and the other axis represents a discrete value. Some bar graphs present bars clustered in groups of more than one (grouped bar graphs), and others show the bars divided into subparts to show cumulative effect (stacked bar graphs). Bar graphs are especially useful when categorical data is being used. (Source: opentextbc.ca)

 

 

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